Many phosphate and phosphorothioate esters are known to have pesticidal activity of one kind or another. Various related sulfur-substituted phosphorothioate esters are known to be active insecticides and miticides. Among such compounds are the dialkyl alkylsulfinylphenyl phosphorothioates and related esters described in U.S. Pat. No. 3,042,703, West German Pat. No. 1,183,494, and Japanese Pat. No. 11880/66. These patents all disclose esters having the structural formula ##STR1## wherein the phenyl group may have one or more inert substituents, R is a lower alkyl group, usually methyl or ethyl, and R' is also a lower alkyl group. These compounds are described in the above patents as active contact insecticides and miticides.